Lanesborough was enfranchised by Charles I in 1642, 17 Chas I, which granted to Sir George Lane and his heirs lands in Co. Longford designated the Manor of Lanesborough with various privileges and franchises including the return of two members to parliament. The Dillons were originally a Catholic family who with difficulty claimed the protection offered by the Articles of Galway. Robert Dillon (0636) conformed before 1728, when he became MP for Dungarvan. They appear to have acquired the borough of Lanesborough about the middle of the century.
Despite its elaborate charter, by the eighteenth century Lanesborough conformed to the usual pattern of a sovereign and burgesses. Thomas Burgh (0281) of Bert was returned for Lanesborough in 1727, and after his death in 1758 there was a certain insecurity in the borough as it was thought that Sir Arthur Gore (0859) might raise a challenge. Sometime previously, John Hely-Hutchinson (1001) made a bargain with Luke Dillon, the father of Robert Dillon (0637), and 'was returned upon an old contract made with the late Mr Dillon for a seat in this Borough during life, on paying £500 on each return. The present Mr Dillon refuses to comply with this engagement.' Hely-Hutchinson sat briefly for Lanesborough during the final session of the parliament of George II. In 1761, when the election for Lanesborough was concluded, the Dublin Journal reported that: '10 Burgesses 74 Freemen voted for William Harwood [Harward, 0986], 84; 10 Burgesses 72 Freemen voted for J. Hely Hutchinson, 82; 1 Burgess 8 Freemen voted for Mr Lane, 9; 1 Burgess 5 freemen voted for Col. Wilmot, 6.' Meanwhile Hely-Hutchinson had decided to sit for Cork city, for which he had also been elected, and Henry Gore was returned in his place. Thereafter the number of freemen appears to have steadily declined, as in 1784 there were 'very few'.263 Dillon appears to have consolidated his position, although in 1776 Hely-Hutchinson's second son, John (1002), was returned; this may have been a compromise as after this election the Hely-Hutchinsons appear to have changed their attention to Taghmon as a back-up.
By 1783 Dillon's control was absolute, and in 1790 it was stated that:
This Borough, whose voters are composed of a select number of Burgesses only, is the sole property of Robert Dillon, Esq. of Clonbrock, whose pleasure creates the electors and appoints the elected. Mr Dillon (0637) being always chosen for one of its seats [he sat for it from 1776 to 1790], the other was long filled by some of the family of the Secretary of State (1001), from a supposed compact of the duration of the Rt Hon. Secretary's life but Mr Dillon having, by a spirited determination, at length freed himself from that engagement, this seat has been since sold to the highest bidder. Both seats will certainly share the same fate, should Mr Dillon succeed in his combat to represent the County of Galway which at present seems the favourite object of his ambition.
However, this was not necessary as in 1790 Robert Dillon was elevated to the peerage as Lord Clonbrock and in 1791 Lanesborough was 'a close Borough, belonging to Lord Clonbrock, who gave the return to Government, for his Peerage. Mr Bushe (0310) Commissioner of the Revenue. Brother-in-law to Mr Grattan (0895). Mr Moore (1479) formerly connected with the Ponsonbys. Treasurer to the Post Office £600. Both good parliamentary men.' Clonbrock died in 1795. In 1800 his son was awarded £15,000 in compensation for the borough's disfranchisement.